The ornamental design for a hearth, as shown and described.
FIG. 1 is a perspective view of a hearth showing a first embodiment of the new design;
FIG. 2 is a back elevational view thereof;
FIG. 3 is a side elevational view thereof, the opposite side being a mirror image of this view;
FIG. 4 is a front elevational view thereof;
FIG. 5 is a top view thereof; and,
FIG. 6 is a bottom view thereof.
The broken line showing of portions of the hearth in FIGS. 2,3,5 and 6 are included for the purpose of illustrating environment and forms no part of the claimed design.